In time we will have a working mathematica of genetics and what willbe clear is that there are specific solutions available that can beused as required. It takes time to implement but it is all there inthe first instance.
We have already understood that an organism transforms itself toenter a new ecological zone. The organism understands or cognatesthe need and implements. Now we are shown that an a far morefundamental level, a problem attracts a solution. These are subtlebut obviously very important.
This works essentially proves the inherent logic underlying allnatural evolution. Survival of the fittest is a mere outcome but nota primary driver. The primary driver is the need to exploit anunfriendly ecology to expand populations.
Far from random,evolution follows a predictable genetic pattern
by Morgan Kellyfor Princeton News
Princeton NJ (SPX)Oct 31, 2012
ThePrinceton researchers sequenced the expression of a poison-resistantprotein in insect species that feed on plants such as milkweed anddogbane that produce a class of steroid-like cardiotoxins calledcardenolides as a natural defense. The insects surveyed spanned threeorders: butterflies and moths (Lepidoptera); beetles and weevils(Coleoptera); and aphids, bed bugs, milkweed bugs and other suckinginsects (Hemiptera). Above: Dogbane beetle (Photo courtesy of PeterAndolfatto)
http://www.terradaily.com/reports/Far_from_random_evolution_follows_a_predictable_genetic_pattern_999.html
Evolution, oftenperceived as a series of random changes, might in fact be drivenby a simple and repeated genetic solution to an environmentalpressure that a broad range of species happen to share, according tonew research.
Princeton Universityresearch published in the journal Science suggests that knowledge ofa species' genes - and how certain external conditions affect theproteins encoded by those genes - could be used to determine apredictable evolutionary pattern driven by outside factors.Scientists could then pinpoint how the diversity of adaptations seenin the natural world developed even in distantly related animals.
"Isevolution predictable? To a surprising extent the answer is yes,"said senior researcher Peter Andolfatto, an assistant professorin Princeton's Department of Ecology and Evolutionary Biology andthe Lewis-Sigler Institute for Integrative Genomics. He worked withlead author and postdoctoral research associate Ying Zhen, andgraduate students Matthew Aardema and Molly Schumer, all fromPrinceton's ecology and evolutionary biology department, as well asEdgar Medina, a biological sciences graduate student at theUniversity of the Andes in Colombia.
Theresearchers carried out a survey of DNA sequences from 29 distantlyrelated insect species, the largest sample of organisms yetexamined for a single evolutionary trait. Fourteen of these specieshave evolved a nearly identical characteristic due to one externalinfluence - they feed on plants that produce cardenolides, a class ofsteroid-like cardiotoxins that are a natural defense for plants suchas milkweed and dogbane.
Though separated by300 million years of evolution, these diverse insects - which includebeetles, butterflies and aphids - experienced changes to a keyprotein called sodium-potassium adenosine triphosphatase, or thesodium-potassium pump, which regulates a cell's crucialsodium-to-potassium ratio. The protein in these insects eventuallyevolved a resistance to cardenolides, which usually cripple theprotein's ability to "pump" potassium into cells and excesssodium out.
Andolfatto and hisco-authors first sequenced and assembled all the expressed genes inthe studied species. They used these sequences to predict how thesodium-potassium pump would be encoded in each of the species' genesbased on cardenolide exposure.
Scientists usingsimilar techniques could trace protein changes in a species' DNA tounderstand how many diverse organisms evolved as a result ofenvironmental factors, Andolfatto said. "To apply this approachmore generally a scientist would have to know something about thegenetic underpinnings of a trait and investigate how that traitevolves in large groups of species facing a common evolutionaryproblem," Andolfatto said.
"For instance,the sodium-potassium pump also is a candidate gene location relatedto salinity tolerance," he said. "Looking at changes tothis protein in the right organisms could reveal how organisms haveor may respond to the increasing salinization of oceans andfreshwater habitats."
Jianzhi Zhang, aUniversity of Michigan professor of ecology and evolutionary biology,said that the Princeton-based study shows that certain traits have alimited number of molecular mechanisms, and that numerous, distinctspecies can share the few mechanisms there are. As a result, it islikely that a cross-section of certain organisms can provide insightinto the development of other creatures, he said."The finding ofparallel evolution in not two, but numerous herbivorous insectsincreases the significance of the study because such frequentparallelism is extremely unlikely to have happened simply by chance,"said Zhang, who is familiar with the study but had no role in it.
"Itshows that a common molecular mechanism is used by many differentinsects to defend themselves against the toxins in their food,suggesting that perhaps the number of potential mechanisms forachieving this goal is very limited," he said. "That manydifferent insects independently evolved the same molecular tricks todefend themselves against the same toxin suggests that studying asmall number of well-chosen model organisms can teachus a lot about other species. Yes, evolution is predictable to acertain degree."
Andolfattoand his co-authors examined the sodium-potassium pump protein becauseof its well-known sensitivity to cardenolides. In order to functionproperly in a wide variety of physiological contexts, cells must beable to control levels of potassium and sodium. Situated onthe cell membrane, the protein generates a desiredpotassium to sodium ratio by "pumping" three sodium atomsout of the cell for every two potassium atoms it brings in.
Cardenolides disruptthe exchange of potassium and sodium, essentially shutting down theprotein, Andolfatto said. The human genome contains four copies ofthe pump protein, and it is a candidate gene for a number of humangenetic disorders, including salt-sensitive hypertension andmigraines. In addition, humans have long used low doses ofcardenolides medicinally for purposes such as controlling heartarrhythmia and congestive heart failure.
The Princetonresearchers used the DNA microarray facility in the University'sLewis-Sigler Institute for Integrative Genomics to sequence theexpression of the sodium-potassium pump protein in insect speciesspanning three orders: butterflies and moths (Lepidoptera); beetlesand weevils (Coleoptera); and aphids, bed bugs, milkweed bugs andother sucking insects (Hemiptera).
The researchers foundthat the genes of cardenolide-resistant insects incorporated variousmutations that allowed it to resist the toxin. During theevolutionary timeframe examined, the sodium-potassium pump of insectsfeeding on dogbane and milkweed underwent 33 mutations at sites knownto affect sensitivity to cardenolides. These mutations often involvedsimilar or identical amino-acid changes that reduced susceptibilityto the toxin. On the other hand, the sodium-potassium pump mutatedjust once in insects that do not feed on these plants.
Significantly, theresearchers found that multiple gene duplications occurred in theancestors of several of the resistant species. These insectsessentially wound up with one conventional sodium-potassium pumpprotein and one "experimental" version, Andolfatto said. Inthese insects, the newer, hardier versions of the sodium-potassiumpump are mostly expressed in gut tissue where they are likely neededmost.
"These geneduplications are an elegant solution to the problem of adapting toenvironmental changes," Andolfatto said. "In species withthese duplicates, the organism is free to experiment with one copywhile keeping the other constant, avoiding the risk that the newversion of the protein will not perform its primary job as well."
The researchers'findings unify the generally separate ideas of what predominatelydrives genetic evolution: protein evolution, the evolution of theelements that control protein expression or gene duplication. Thisstudy shows that all three mechanisms can be used to solve the sameevolutionary problem, Andolfatto said.
Central to the work isthe breadth of species the researchers were able to examine usingmodern gene sequencing equipment, Andolfatto said.
"Historically,studying genetic evolution at this level has been conducted on just ahandful of 'model' organisms such as fruit flies," Andolfattosaid. "Modern sequencing methods allowed us to approachevolutionary questions in a different way and come up with morecomprehensive answers than had we examined one trait in any oneorganism.
"The power ofwhat we've done is to survey diverse organisms facing a similarproblem and find striking evidence for a limited number of possiblesolutions," he said. "The fact that many of these solutionsare used over and over again by completely unrelated species suggeststhat the evolutionary path is repeatable and predictable."
Thepaper, "Parallel Molecular Evolution in an Herbivore Community,"was published Sept. 28 by Science. The research was supported bygrants from the Centre for GeneticEngineering andBiotechnology, the National Science Foundation and the NationalInstitutes of Health. This research was published in thejournal Science.
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